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Comparison of Meteorological Elements in Dry and Wet Seasons and Parameterization of Momentum and Sensible Heat Exchange Coefficients near the Underlying Surface of the Zhuhai Phoenix Mountain Forest
2020,25(5):457-468, DOI: 10.3878/j.issn.1006-9585.2019.19027
Abstract:The variation characteristics of the energy flux and meteorological elements of the underlying surface of the forest during the wet and dry seasons were compared and analyzed by using observation data obtained from November 2014 to May 2016 from the Zhuhai Phoenix Mountain Land-Atmosphere Interaction Observation Tower Station. The variation characteristics of the momentum and sensible heat exchange coefficients in three wind direction ranges (315°-45°, 45°-135°, and 135°-225°) along with the canopy-surface wind speed under different stability conditions, as well as the parameterizations of these coefficients were analyzed. The sensible heat and latent heat fluxes in the dry season were equivalent, whereas in the wet season latent heat is much higher than the sensible heat. Negative sensible heat occurs during the night in both the dry and wet seasons, with the sensible heat being transported from the atmosphere to the forest. The variation range of the relative humidity is large and is closely related to the meteorological conditions in the area. The vertical gradient of the relative humidity is larger at night and smaller during the day. The vertical gradient of the air temperature in the dry season is more significant than that in the wet season. The wind speed changes gently in winter but violently in summer. There is an obvious gradient in the low-level wind speed with height, whereas the high-level wind is chaotic. The wind direction at different heights does not differ significantly. In neutral and near-neutral states, the momentum exchange coefficients Cdn are 0.05, 0.0055, and 0.022, respectively, when the wind directions are 315°-45°, 45°-135°, and 135°-225°, and the sensible heat exchange coefficients Chn are 0.0055, 0.003, and 0.004, respectively. Under stable and unstable conditions, the momentum exchange coefficient Cd and the sensible heat exchange coefficient Ch obviously change with the wind velocity v on the canopy surface. Under stable conditions, Cd and Ch increase with increases in v, and under unstable conditions, Cd, and Ch decrease with increases in v. We fitted the relationships between Cd, Ch in the forest canopy and v under stable and unstable conditions in different wind directions, and obtained the parameterized formula.
2020,25(5):469-482, DOI: 10.3878/j.issn.1006-9585.2020.19100
Abstract:The mechanisms involved in the development of high temperature anomalies in Northeast China during the summer of 2018 were studied using observational and reanalysis data. First, daily temperatures recorded at observation stations in the region throughout the summer were analyzed. Next, the excess heat factor index of the observation stations was calculated. July and August were the main anomaly high temperature periods when high temperature anomalies occurred in the southern part of Northeast China. The South Asia high (SAH) and western Pacific subtropical high (WPSH) were significantly intensified during this period, and overlapped with each other on different levels and extended northward. There was also an increase in the negative vorticity anomalies in the overlapping area of the SAH and WPSH, and the two northward extending systems continued to drive the negative vorticity anomalies. In addition, an abnormal down draft occurred over the southern part of Northeast China together with sinking adiabatic warming and clear-sky radiation warming, which may have been important factors involved in surface warming in this area. Furthermore, surface temperature anomalies were significantly correlated with negative vorticity anomalies at geopotential heights from 300 to 500 hPa during the summer of 2018 in this region. It was also determined that the quasi-stationary Rossby wave energy propagation in the summer subtropical westerly jet was closely related to the anomalous enhancement of the SAH and WPSH. Significant simultaneous warming of the western Pacific warm pool during the summer also promoted unusually strong convective activity in the Philippines. The Pacific-Japan (PJ) wave train was excited at a geopotential height field of 500 hPa, which also led to the enhancement and northward extension of the WPSH. In summary, the existence of the SAH and WPSH and their overlapping were the main causes of the high temperature anomalies in the southern part of Northeast China during July and August 2018.
Temporal and Spatial Distribution Characteristics and Influencing Factors of Pan Evaporation in China from 1961 to 2013
2020,25(5):483-498, DOI: 10.3878/j.issn.1006-9585.2019.19130
Abstract:Based on pan evaporation (PE) observations at 1302 weather stations in China for 1961-2013, in this paper, we present our analysis of the temporal and spatial characteristics and their impact on the climate factors of PE. The results indicate that both the annual and seasonal mean PE values from all stations show a significant downward trend, with an abrupt change occurring in 1978. The stations with a significant downward PE trend are mainly located in the North China Plain, Xinjiang, Guangdong, Guangxi, and Hainan provinces, whereas PE shows a significantly increasing trend in Fujian, Zhejiang, and Guizhou provinces. We performed empirical orthogonal function (EOF) analyses of the annual PE anomalies. For the first mode (EOF1), the time coefficient changes from positive to negative in 1981, and the variation of the EOF1 spatial pattern is similar as that of PE magnitude. The EOF2 mode presents opposite patterns in South and North China and after 2002, the PE decreased in North China, but increased in South China. Additionally, we calculated the partial correlation coefficients between PE and five climate elements, including precipitation, temperature, surface wind speed, relative humidity, and sunshine duration. The results show that except for precipitation, the other four variables are very well correlated with PE. The correlation between wind speed and PE is significantly positive, and the regions with the highest correlation are consistent with those with the largest EOF1 variability. The correlation between humidity and PE is significantly negative. The correlation between temperature and PE are positive overall, with the largest values appearing in areas where PE increases. The correlation coefficients between the sunshine duration and PE are greater than 0.6 in three seasons but not in spring. Moreover, we found that the linear trends of both wind speed and sunshine duration greatly impact their relationships with PE. Thus, we conclude that a decreasing trend in PE is largely because of decreasing wind speed and sunshine duration. Furthermore, when drought occurs, PE increases significantly, and the changes in precipitation, temperature, relative humidity, and sunshine duration also significantly contribute to the increases in PE. As such, PE could be a good indicator of drought.
Effectiveness of Air Pollution Control Efforts in Beijing-Tianjin-Hebei Region during 2013-2018 Based on the Kolmogorov-Zurbenko Filter
2020,25(5):499-509, DOI: 10.3878/j.issn.1006-9585.2020.19094
Abstract:China’s air quality has improved in recent years by the implementation of strict pollution control action plans such as the National “Ten Measures for Air” ratified by the Chinese State Council. To achieve sustained improvements in air quality and targeted pollution control in the coming years the effectiveness of these pollution control initiatives must be scientifically evaluated. Because air quality levels are strongly influenced and at times even dominated by meteorological conditions, a major difficulty of such analysis is quantifying the contributions of meteorological conditions and pollution control initiatives to variations in the respective pollutant concentrations. In this study, we assessed the effectiveness of pollution control efforts for one of the most heavily polluted areas in China—the Beijing-Tianjing-Heibei region—by analyzing (1) the time-frequency properties of the PM2.5 time series collected from 86 monitoring sites in 13 cities of this region during 2013-2018 and (2) the corresponding meteorological conditions retrieved from the reanalysis product of the European Center for Medium-range Weather Forecast (ECMWF). We used the Kolmogorov-Zurbenko filter to separate the original PM2.5 series into three components: Short-term weather-related variations, medium-term seasonal variations, and long-term trends. We constructed regression models to account for the influence of meteorological variables on the PM2.5 concentrations to distinguish their impacts on pollution abatement from those of the emission reduction actions. We found that during 2013-2018, the long-term trends of PM2.5 concentration over 13 cities decreased significantly (22.2%-58.0%), with Xingtai city experiencing the greatest decrease (58.0%). Both meteorological conditions and emission reduction actions contributed to the improvement of air quality, but emission reduction actions were the decisive factor in the significant improvement in air quality. The contributions of meteorological conditions and emission reduction actions were 18.5% and 81.5%, respectively. Among the 13 cities, the meteorological conditions were the most beneficial for Tangshan (29.2%) whereas emission reduction actions played the most important role for Hengshui (92.0%).
Circulation Anomaly and Sea Surface Temperature Forcing in Rare Continuous Rainy Weather in Zhejiang during the Winter of 2018/2019
2020,25(5):510-520, DOI: 10.3878/j.issn.1006-9585.2019.19060
Abstract:Based on the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) global reanalysis data, ground observation data, and automatic station precipitation data, this study analyzed circulation anomalies such as winter monsoon circulation and the South Branch trough in rare continuous rain and oligoscale weather in Zhejiang in the winter of 2018/2019. Moreover, the study investigated the causes of local circulation anomalies from aspects such as westerly wind fluctuation and sea temperature forcing. The results showed that in the winter of 2018/2019, the rainy days and sunshine hours surpassed the historical record, and the rainfall was significantly above normal. The main circulation anomalies were the abnormal northerly western North Pacific anomalous anticyclone (WNPAC). Meanwhile, the Aleutian low-pressure and the Siberian high-pressure systems were also northerly. There was a strong southerly wind anomaly south of 40°N in East Asia, and the winter monsoon was weak. The southern branch trough was stronger than the perennial, ensuring that there was a continuous water vapor and disturbance transport over Zhejiang. In the middle layer of the troposphere, a wave energy propagated along Europe to East Asia and the western Pacific. The wave energy spread southward to the south of 20°N in East Asia, which might lead to a significant north lift of the WNPAC and the strengthening of the southern branch trough. The El Niño-Southern Oscillation (ENSO) warm phase caused abnormal convective cooling in the maritime continent, while the convection over Zhejiang strengthened, and ENSO also had a significant effect on the activity intensity of the southern branch trough. The high sea surface temperature in the offshore waters of China was an important factor for the WNPAC and the Aleutian Low to significantly jump north. The abnormal circulation in the northern hemisphere in the winter of 2018/2019 might have been caused by ENSO and China’s offshore sea temperature collaborative forcing.
2020,25(5):521-530, DOI: 10.3878/j.issn.1006-9585.2019.19114
Abstract:In this study, Beijing is selected as the research area to perform wind speed correction of the aerosol optical depth (AOD) data of the 440 nm band inversion of the CE-318 solar photometer provided by AERONET (Aerosol Robotic Network) in 2014-2017. Then, the seasonal correlation analysis and modeling of the corrected daily average AOD data and the same period ground monitoring station daily average PM2.5 concentration data are conducted. Then, the visibility factor is introduced and the generalized difference method is used to construct the ternary regression model of AOD, PM2.5, and visibility in Beijing from 2015 to 2017. Finally, the data of 2014 are divided into pollution and nonpollution days for the model tests. Results show a significant linear positive correlation between AOD and PM2.5. Moreover, the seasonal differences exhibit the strongest correlation in summer, followed by that in autumn, and the weakest correlation in spring and winter. After introducing the visibility factor and eliminating the autocorrelation, the relative error of the model in the four seasons is reduced, the goodness of fit of the model significantly improved, and the relative error ranges from 21% to 31%. Compared with the previous results, the accuracy of curve fitting has been significantly improved. Moreover, the simulation effect of the model is good for low PM2.5 concentration days but poor for high PM2.5 concentration days. This study is of scientific significance for the construction of the long-term historical data of PM2.5 in Beijing.
2020,25(5):531-542, DOI: 10.3878/j.issn.1006-9585.2020.19185
Abstract:Based on the daily precipitation, relative humidity, and air temperature data during 1961-2017 from 96 stations in Northeast (NE) China, through trend analysis and the Mann-Kendall test method, the climate change characteristics of light rainfall, moderate rainfall, heavy rainfall, and torrential rainfall in summer and the causes of the decreasing trend of light rainfall frequency over NE China are analyzed. The main results are as follows: A significant positive correlation exists between the total precipitation over NE China and all types of precipitation frequency and contribution, and the total precipitation is mainly influenced by the frequency and contribution of heavy rain. The decrease in light rainfall and moderate rainfall is the main cause of the decrease in total precipitation in summer over NE China, and the torrential rainfall influenced by the increase in the torrential rainfall contribution shows a rising tendency. Furthermore, an interdecadal abrupt change in light rainfall and light rainfall contribution occurred around 1993, and the interdecadal abrupt change in light rainfall contribution has resulted in the interdecadal abrupt change in light rainfall. A certain decreasing trend of the total precipitation at 72 stations over NE China 85 stations showed a certain decreasing trend of the light rainfall, among which 25 stations show a significant decreasing trend; moreover, 70 stations show a certain decreasing trend of moderate rainfall, among which only nine stations show a significant decreasing trend; the number of stations that show an increasing trend of heavy rainfall is comparable to the number of those that show a decreasing trend, and the number of stations that show an increasing trend of the torrential rainfall is greater than the number of those that show a decreasing trend. Regarding cloud formation, the effects of the changes in water vapor, temperature, and aerosol concentration on the reduction in light rainfall in NE China are analyzed. The results show that the global temperatures rising and increased aerosol concentration are the main causes of the decreasing light rainfall in NE China.
Changes in Vegetation Growing Season and Active Accumulated Temperature in Circum-Arctic Region under 21st Century Climate Change Scenario
2020,25(5):543-554, DOI: 10.3878/j.issn.1006-9585.2020.20014
Abstract:Based on Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) downscaling data of simulations generated by five climate (Earth) system models in CMIP5, in this study, the multi-model collection was used to estimate the vegetation growing season and active accumulated temperature changes in the circum-Arctic region in the 21st century under various climate change scenarios. The research results show that: 1) Multi-model ensemble simulation can basically reproduce the observed spatial distribution characteristics of the initial and final frost days, length of the frost-free period, accumulated temperature of >10℃, and change trends of these indicators from 1979 to 2004. However, its ability to simulate the spatial differences and interannual variability of climate change is weak. 2) By the end of the 21st century, the final frost day will advance by up to 60 days, initial frost day will be delayed by 20-40 days, frost-free period will extend up to 100 days, and accumulated temperature will vary by 1000-1200℃. Each of these indicators undergoes the greatest change under the RCP8.5 scenario, and the least change under the RCP2.6 scenario. 3) The changes in the indicators have large spatial differences, with the changes in the central and western parts of the Eurasian continent being generally larger. With the warming of the climate, increases in the accumulated temperature>10℃ gradually show obvious zonality in the latitudinal direction, with a greater increase in the south.
2020,25(5):555-574, DOI: 10.3878/j.issn.1006-9585.2020.20025
Abstract:This study aims to evaluate the effect of two, new, global soil datasets on global land surface simulation, based for the first time on the Common Land Model (CoLM). The effects of the two soil datasets, namely GSDE (Global Soil Dataset for Earth System Model) and Soil Grids (SG), on the model simulation results were studied. The differences between these two data sets were compared and analyzed for five soil properties, namely sand, clay, gravel, organic carbon, and bulk density, and the impact, caused by those differences, on the estimated soil characteristic parameters as well as the hydraulic and thermal variables in the model were discussed. The results show that the global spatial distribution of soil characteristic parameters is mainly influenced by soil particle size distribution (sand, silt, and clay), and also by gravel, organic matter, and bulk density. The effect of the soil datasets on the global simulation varies across different regions. Their effect on the hydrological variables (the maximum value of Re is ±100%) is greater than that on the soil thermodynamic variables (Re<±10%) and on the surface radiation variables (Re<±5%). The soil volumetric water content in central and northwest Canada, southeastern Russia, and midwest and central Australia is quite different, and the total runoff in low latitudes area shows great variance. Thermal variables show some differences in northern Africa, northwestern Canada, and north-central Russia. Comparing the simulated soil moisture with site observations, the performance of the two datasets is similar and there is a certain deviation from the site observations. More specifically, the values based on the SG data are closer to the observation values. The results show that there is an increase of about 0.01 to 0.02 using the SG data compared with the GSDE data at the Molly Caren site. This study shows that the model simulation results are significantly affected by different datasets and that soil data with higher accuracy, such as the SG data, are preferable for model use. Further studies on the effect of soil properties on land surface modeling are required.
Volume 25,2020 Issue 5
Linear trends in high temperature and heatwave occurrence in China for the period 1960~2018: analysis method and results
Available online:January 19, 2020 DOI: 10.3878/j.issn.1006-9585.2019.19134
Abstract:High temperature and heatwave (HT and HW) directly impact human health and crop growth. Investigating the trends in the occurrence of HT and HW is one of the fundamental questions of climate change research and can provide valuable information for living and production. Most of the previous studies on trends in the occurrence of HT and HW used ordinary least squares (OLS) method to calculate the magnitude of linear trend and then used student’s t-test to determine the statistical significance of this trend. This study examined whether traditional methods are suitable for the trend estimation of the occurrence of HT and HW in China. By showing a case of the annual count of HT days with extremely excessive occurrences in 2018 at a station in northeastern China, we illustrated that OLS method is sensitive to outliers and can give spurious trend. Further, through normality testing and autocorrelation calculation, we found at least 91.14% of stations and 90.06% of grid boxes for the annual count of HT days and 92.18% of stations and 87.74% of grid boxes for the annual count of HW in China are non-Gaussian, and the majority of them have serial correlation. Applying a nonparametric method that is insensitive to outliers and takes into account serial correlation, we gave a more accurate estimation of the linear trends in the annual count of HT days and HW for every station and grid box, four typical regions average, and China area-average for the period 1960~2018. The results show that stations with statistically significant increasing trend in HT days occurred mainly in South China and northwestern China, and those in HW occurred nearly only in South China and several stations in Xinjiang Autonomous Region. In terms of area average of the trend in annual count of HT days and HW, only South China region and northwestern China region show statistically significant increasing trend, whereas North China and northeastern China not significant; those of China average are both significant. This study provides referential information for the choice of method in the estimation of trend and its statistical significance and in statistical prediction for HT days and HW.
Multi-timescale features for surface air temperature in the source region of the Yellow River during 1953-2017
Available online:November 05, 2019 DOI: 10.3878/j.issn.1006-9585.2019.19026
Abstract:Abstract: Based on the annual averaged surface air temperature data from eight meteorological stations in the source region of the Yellow River using the Ensemble Empirical Mode Decomposition (EEMD) approach, the multi-timescale temperature features of meteorological stations with Madoi as a representative during 1953-2017 and their contributions to the temperature variations are revealed. The correlations between different time-scale temperature oscillations with the SST indices are analyzed, particularly with the Atlantic Multidecadal Oscillation (AMO). The results demonstrated that: (1) a long-term temperature trend was 0.31℃/10a during 1953-2017 in the source region of the Yellow River, and the warming started in the late 1980s and accelerated in the late 1990s. (2) There were 3-year, 6-year, 11-year, 25-year, 64-year and 65-year quasi-cycle oscillations for the temperature during 1953-2017. Among them, the 3-year and 65-year quasi-cycle oscillations were significant. The amplitude of 3-year time-scale oscillation was large before the 21st century and decreased after the 21st century, while the amplitude of 65-year oscillation was enhanced after the 21st century. (3) The 3-year quasi-cycle oscillation occupied a dominant position during the period of 1953-1997, and the contribution of 65-year oscillation increased nearly five times which was equivalent to the contribution of the 3-year oscillation during the rapid warming period since 1998. (4) The correlations between temperature with Nino3.4 and PDO indices were not significant, but the maximum significant correlation was found when the temperature led PDO 22 years. Unlike PDO, the maximum significant correlation was found when AMO led the original temperature and its three inter-decadal components 0 and 3-7 years which supported that AMO had a significant impact on the temperature variation in the source region of the Yellow River. (5) The positive warm phase of AMO corresponded to the warming of the East Asia including China, and the source region of the Yellow River was only a part of that area. The negative cold phase of AMO from the early 1960s to the middle and late 1990s and the positive warm phase of AMO from the early 1990s to the present corresponded to the negative and positive phases of the temperature in the source region of the Yellow River. The AMO highly correlated with the 65-year oscillation. These results supported that AMO was an important climatic oscillation affecting the temperature variation especially on the inter-decadal time scales in the source region of the Yellow River.
Development of a Meteorology-Chemistry Two-Way Coupled Numerical Model (WRF-NAQPMS) and Its Application in a Severe Autumn Haze Simulation over the Beijing-Tianjin-Hebei Area, China
2014,19(2):153-163, DOI: 10.3878/j.issn.1006-9585.2014.13231
Abstract:An aerosol-optical module based on Mie scattering theory has been implemented in the Nested Air Quality Prediction Modeling System (NAQPMS), and a new coupler has been developed to deal with the interaction between the mesoscale meteorology model WRF (Weather Research and Forecasting Model) and NAQPMS. The one-way off-line and two-way coupled WRF-NAQPMS models are compared to simulate the severe haze in the Beijing-Tianjin-Hebei area from 27 September to 1 October 2013. The results show that the simulated meteorological elements and PM2.5 concentrations from the two-way coupled model with the aerosol direct radiation effect are more consistent with observations. During the haze period, the boundary layer meteorological elements change significantly because of the aerosol direct radiation effect over the Beijing-Tianjin-Hebei area: Incoming solar radiation is reduced by 25%, the 2-m temperature decreases by 1 ℃, the turbulent kinetic energy is reduced by 25%, the 10-m wind speed decreases by up to 0.2 m/s, and the planetary boundary layer (PBL) height is reduced by 25%. These changes make the atmospheric boundary layer more stable and further exacerbate air pollution over the areas where it is already severe, for example, the PM2.5 concentration increases by up to 30% over Shijiazhuang City. The analysis indicates that there is a positive feedback mechanism between haze and boundary layer meteorology, and the two-way coupled model incorporating this feedback is helpful for accurate simulation and forecasting of haze pollution processes.
2008,13(2):123-134, DOI: 10.3878/j.issn.1006-9585.2008.02.02
2010,15(4):337-353, DOI: 10.3878/j.issn.1006-9585.2010.04.01
Variations of the Sea Surface Temperature in the Offshore Area of China and Their Relationship with the East Asian Monsoon under the Global Warming
2011,16(1):94-104, DOI: 10.3878/j.issn.1006-9585.2011.01.09
Abstract:Based on the long time series of mean Sea Surface Temperature (SST) and high-resolution wind field reanalysis data such as HadISST and ERA-40 reanalysis data, the variations of the SST in the offshore area of China and their relationship with the East Asian Monsoon (EAM) in winter (December to the next February) and summer (June to August) are analyzed using the Empirical Orthogonal Function (EOF) and linear regression analysis methods. The results show that: 1) The SST in the offshore area of China in winter or summer exhibited significant interannual and interdecadal variations, and experienced a climate shift in the mid-1980s. The areas with the strongest increase in SST are located in the East China Sea (ECS) in winter and in the Yellow Sea in summer. The SST increased by 1.96°C in winter for the period of 1955-2005 and 1.10 °C in summer for the period of 1971-2006. 2）The EAM has displayed distinct interannual and interdecadal variations with a weakening trend since the end of the 1980s in winter, and since the end of the 1970s in summer. In addition, the linear regression analysis indicates the relationship of the SST to EAM in winter on interdecadal timescale is closer than that on interannual timescale. The interdecadal weakening trend of EAM in winter contributes to the rise in SST in the offshore areas of China, particularly significant in the ECS. Moreover, the related areas of winter or summer mean SST on the interannual timescale in the offshore area of China to the EAM are located in the South China Sea (SCS), and the relationship in winter is much more obvious than that in summer. It is found that the interannual variation of SST in the SCS has obvious relation to the anomalies of the meridional southward and northward winds over the SCS and zonal migration of the subtropical anticyclone over the western Pacific.
2011,16(6):733-741, DOI: 10.3878/j.issn.1006-9585.2011.06.07
Abstract:A field performance of Doppler wind lidar Windcube (released by Leosphere Company) was conducted by Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) and Leosphere Company (from France) at the 325 m meteorological tower site (a part of IAP, located between 3rd North Ring Road and 4th North Ring Road) from 11 December to 14 December 2007. The intercomparison of wind speed and wind direction obtained by Windcube and wind cup anemometers (fixed in the meteorological tower) shows that：1) 10 min averaged wind speed is highly consistent between two types of wind data at six matched levels (63 m, 80 m, 100 m, 120 m, 160 m, and 200 m), the correlation coefficients all equal or exceed 0.98. 2) 10 min averaged wind direction is calculated with the vector method, the correlation coefficients of averaged wind direction at the six levels are 0.99. 3) In comparison with domestic Doppler wind lidar, Windcube performs slightly better in wind speed measuring, and equally well in wind direction measuring. The intercomparison indicates that Windcube is a reliable and swift mobile system mea suring wind profile at low levels.
2006,11(1):14-32, DOI: 10.3878/j.issn.1006-9585.2006.01.02
2009,14(1):69-76, DOI: 10.3878/j.issn.1006-9585.2009.01.08
Abstract:作为酸雨和细粒子的前体物，SO2对空气质量和人体健康乃至气候与环境的影响十分重要，特别是在不利于扩散的气象条件下，SO2可造成城市短时间严重污染事件。作者以2006年北京325 m气象塔15 m观测平台SO2观测数据为基础，结合同步气象资料分析研究发现：1) SO2浓度冬季高、夏季低；全年日均值为(22.5±22.1)×10-9，最大日均值能达到113×10-9。日变化呈现双峰型，峰值出现在北京时间08:00和22:00；并且季节差异明显，冬季浓度为夏季的4.5倍，采暖期为非采暖期的3.2倍。2) 风向、风速与SO2扩散和输送密切相关，高浓度SO2在东北、东、西方向上出现频率分别为25.8%、13.8%和11.8%；而西北、北方向上的风速越大对SO2清除效果越好。3)利用平均晴空指数划分采暖期阴霾天和晴天，发现阴霾天混合层高度与平均风速仅为(376±204) m和1.1 m·s-1，容易造成SO2累积。4) SO2污染过程呈现周期性的局地累积—清除特征，地形、静风和暖低压是造成北京2006年1月一次重污染事件的成因。
The Mutual Response between Dynamical Core and Physical Parameterizations in Atmospheric General Circulation Models
2011,16(1):15-30, DOI: 10.3878/j.issn.1006-9585.2011.01.02
Abstract:A study of the interaction and mutual response between dynamical core and physical parameterizations by atmospheric general circulation models CAM3.1 and IAP AGCM4.0 is presented. Both the two models were integrated 60 d with ideal physics (Held-Suarez forcing) and with full physical package, respectively. The results show that the mutual responses between dynamical core and physical parameterizations are very different in the troposphere at low latitudes and high latitudes. In the tropical troposphere, the variability of temperature tendency due to dynamical core and that due to physical parameterizations are both large and have significant contributions to the variability of total temperature tendency, and they are in inverse correlation to compensate each other. In the polar middle and upper troposphere, the variability of total temperature tendency mainly relies on the tendency due to dynamical core, while the variation of temperature tendency due to physics is very slow, which can be seen as a stationary forcing. Unlike the tropical regions, there is a positive correlation between the temperature tendency due to dynamics and that due to physics in Polar regions. Moreover, the interactions and mutual responses between the individual physical parameterizations are also analyzed. The results show that the variation of temperature tendency due to moist process is the largest of all the physical parameterizations, and it contributes most to the total temperature tendency due to physics. The variation of temperature tendency due to long wave radiation is also large at high latitudes, while the variation of temperature tendency due to short wave radiation and that due to vertical diffusion are relatively small. There is a negative feedback between the cooling rate of long wave radiation and the heating rate of short wave radiation.
1999,4(1):98-103, DOI: 10.3878/j.issn.1006-9585.1999.01.21
2004,9(2):278-294, DOI: 10.3878/j.issn.1006-9585.2004.02.05
A Comparison of NCEP/NCAR, ERA-40 Reanalysis and Observational Data of Sensible Heat in Northwest China
2009,14(1):9-20, DOI: 10.3878/j.issn.1006-9585.2009.01.02
Simulation of Potential Vegetation Distribution and Estimation of Carbon Flux in China from 1981 to 1998 with LPJ Dynamic Global Vegetation Model
Abstract:The LPJ DGVM (Lund Potsdam Jena Dynamic Global Vegetation Model), which is a process based model, is used to simulate the vegetation distribution and estimate the interannual variation of net primary production (NPP), heterotrophic respiration (Rh) and net ecosystem production (NEP)in China from 1981 to 1998. It is shown that there are six main plant functional types (PFTs) besides the desert,that is tropical broadleaved evergreen tree, temperate broadleaved evergreen tree, temperate broadleaved summergreen tree, boreal needleleaved evergreen tree, boreal needleleaved summergreen tree and C3 perennial grass. In China, the total NPP varies between 2.91 Gt·a-1(C) (1982) and 3.37 Gt·a-1(C) (1990), increases by 0.025 Gt (C) average per year and has an increasing trend of 0.96%. The total Rh varies between 2.59 Gt·a-1(C) (1986) and 319 Gt·a-1(C)(1998), grows by 1.05% per year and by 0.025 Gt(C) per year. The linear trend of NPP and Rh for C3 perennial grass is more remarkable than those for other PFTs. The simulation of NEP is reasonable when the fire is brought in the model. Annual total NEP varies between -0.06 Gt·a-1(C)(1998)and 0.34 Gt·a-1(C)(1992). It is demonstrated that the terrestrial ecosystem is carbon sink in China. The above results are similar to those simulated by other models.
Variation Characteristics of the Sunshine Duration and Its Relationships with Temperature，Wind Speed，and Precipitation over Recent 59 Years in China
2011,16(3):389-398, DOI: 10.3878/j.issn.1006-9585.2011.03.14
Abstract:Using the data of sunshine duration, temperature, wind speed， and precipitation from 194 basic/reference stations over China from 1951 to 2009, according to the climatic division, the whole domain of China is classified into 11 climatic regions. The authors studied the changes in annual and seasonal trends of the sunshine duration by using linear trend analysis and Morlet wavelet analysis, and analyzed the characteristics between the sunshine duration and the temperature, the wind speed, and the precipitation. It was found that the annual sunshine duration showed a significant decreasing tendency during the recent 59 years with a decreasing rate of 36.9 h·(10 a)-1. The trend variations of the annual sunshine duration in 11 climatic regions were similar with that in the whole nation, only had the difference in degree. The sunshine duration of China changed from intensive to weak in 1981. There is an obvious 7－10-year periodic oscillation for the annual sunshine duration of China before the mid 1990s. The sunshine duration of the four seasons had a bigger decreasing amplitude in the coastal areas than in the inland areas, and in the South than in the North. There was a negative correlation between the annual sunshine duration and the temperature (correlation coefficient is -0.52), but a positive correlation between the annual sunshine duration and the wind speed (correlation coefficient is 0.76), and a negative correlation between the annual sunshine duration and the precipitation (correlation coefficient is -0.27). The first two correlation coefficients and the last correlation coefficient passed 99.9% and 95% confidence levels，respectively.
Cause and Anomalous Characteristics of the South China Sea Monsoon Trough Producing Heavy Rainfall in South China
2011,16(1):1-14, DOI: 10.3878/j.issn.1006-9585.2011.01.01
Abstract:Atmospheric processes associated with the South China Sea (SCS) monsoon trough which caused the heavy rainfall in pentad 3 of August 2007 in South China are analyzed using the reanalysis data of NCEP and satellite images. The results indicate that the Asian summer monsoon trough has independent space structure, convergence in the low layers and divergence in the high layers are in the south of the Asian summer monsoon trough. The climate analysis shows that both the Indian monsoon trough and the SCS monsoon trough reach their maximum in 〖JP2〗August. The SCS monsoon trough in pentad 3 of August 2007 was located in South China coastal areas and had strong intensity. The convergence in the low layers and divergence in the high layers were also stronger. The Indian monsoon trough was also stronger. The strengthened South Asian high locating over the Tibetan Plateau is the main cause for the strengthening of the Asian monsoon trough. The subtropical high in the western Pacific is located over Japan and is intensified, which is propitous to the northward 〖JP〗movement and the enhancing of the SCS monsoon and monsoon trough. The increased temperature over the Tibetan Plateau induces the stronger easterly in the upper levels, westerly in the low levels,and the enhancing convergence in the low layers and divergence in the high layers of the SCS monsoon trough. The long wave trough in the westerly belt is intensified and extends to Southwest China, which causes the SCS monsoon trough to become stronger. The SCS monsoon trough has an intraseasonal period. The intraseasonal oscillation has an important effect on the northward movement and enhancement of the SCS summer monsoon trough.
2011,16(1):47-59, DOI: 10.3878/j.issn.1006-9585.2011.01.05
Abstract:Based on the MODIS observations, the performance of Interactive Canopy Model(ICM), a dynamic vegetation model including the carbon and nitrogen cycles of the terrestrial ecosystem, has been assessed. The Leaf Area Index (LAI), a key parameter with seasonal variation in vegetation dynamics, is simulated by ICM and compared with the MODIS data. The results show that ICM can simulate the main characteristics of the seasonal LAI fluctuations. Compared to the observation, LAI is overestimated in high and low latitudes, but underestimated in middle latitudes by the model. The underestimation of the LAI in middle latitudes is followed by the vegetation sprout for the reason that the modeled growth is always slower than the observed one. The bimodal distributions for the tropical evergreen broadleaf trees and crops have not been well captured. In addition, the simulated results for the grassland are more reasonable than other Plant Function Types (PFTs). The results will provide important clues for the parameterization improvement and parameters optimization of the ICM.
2008,13(1):75-83, DOI: 10.3878/j.issn.1006-9585.2008.01.10
Combination of Wavelet Decomposition and Least Square Support Vector Machine to Forcast Atmospheric Ozone Content Time Series
2010,15(3):295-302, DOI: 10.3878/j.issn.1006-9585.2010.03.09
Abstract:The atmosphere ozone content forecast model was established based on the combination of wavelet decomposition and advanced Least Square Support Vector Machine (LSSVM) regression. This can be approached in three steps: (1)The observations were decomposed into several different frequency signal subsets,(2)the independent prediction models of decomposed signals with Takens delay embedding theorem and Least-Squares Support Vector Machine (LSSVM) were set up, (3)independent predicted results were integrated as the final prediction with wavelet reconstruction. Application experiments with data from Xianghe and the other three observation stations show that the method can make better prediction effectively for the atmospheric ozone content, as compared with conventional Support Vector Machine(SVM) and Artificial Neural Network(ANN).
A Research on the Application of Spatial Difference Method in Quality Control of Surface Meteorological Data
2010,15(3):229-236, DOI: 10.3878/j.issn.1006-9585.2010.03.02
Abstract:A new Quality Control（QC）technique called spatial difference method is introduced in detail and applied to spatial checking of some basic meteorological elements at seven representative stations in China for the year of 2007 in order to evaluate the applicability of this approach．The checking tests are conducted on ten basic meteorological elements including daily mean pressure，maximum pressure，minimum pressure，mean temperature，maximum temperature，minimum temperature，mean vapor pressure，mean surface temperature, maximum surface temperature, and minimum surface temperature．It is shown that this method works well in identifying errors of single meteorological element．As compared with spatial regression test on discriminating artificial errors，the spatial difference method is more effective．Furthermore，same as the other spatial checking methods，the distribution of neighboring weather stations should be concerned necessarily as influence factors．
2002,7(2):209-219, DOI: 10.3878/j.issn.1006-9585.2002.02.08
2010,15(5):541-550, DOI: 10.3878/j.issn.1006-9585.2010.05.02
Abstract:The Nested Air Quality Prediction Modeling System (NAQPMS) has been applied to the routine air quality forecast in Beijing during the Olympic Games. Monte Carlo method is used to analyze the uncertainty of ozone simulation of NAQPMS during the Olympic Games, from 8 to 24 Aug 2008. Latin hypercube sampling has been used for multi-variables sampling, and 50 ensemble runs have been made with 154 parameter uncertainties being considered together. By the temporal average, the most important parameter to the surface ozone output uncertainty in Beijing is the local precursor emissions during the day time. Other important factors include NO2 photolysis coefficient, wind direction, precursor emissions from the surrounding areas of Beijing, and vertical diffusion coefficient. The wind direction and precursor emissions from the surrounding areas of Beijing have the greatest impact on the uncertainty of daytime ozone simulation at higher levels (above about 150 m). The main uncertainty factors in ozone simulation at night are local NOx emissions and vertical diffusion coefficient. Given the predefined input uncertainties, the average uncertainty of ozone simulation is 19 ppb, ranging from 2 ppb to 49 ppb.
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Editor in chief: 李崇银